1. Field of the Invention
The present invention relates to a device for retaining knife blades for cutting, perforation or other treatment of a running web, preferably a paper web, whereby said web runs between a rotatable knife-retaining cylinder and a counter pressure cylinder knife blade cooperates with a wedge device which is adapted to wedge up said knife blade in a slot in the knife-retaining cylinder. Thus, knife blade can be wedged up by means of the wedge device by being brought into the slot by means of the counter pressure cylinder. The wedge device cooperates with a height-adjustment device which is adapted to permit setting of said wedge device at such height in the slot that said wedge device is able to wedge up a knife blade of a certain defined dimension. The wedge device comprises two rulers having downwardly inclined wedge surfaces relative to the slot. The wedge device preferably comprises at least one spring means which is provided to affect the rulers in vertical direction relative to each other in order to retain said rulers and the knife blade in the slot until they are wedged up therein.
2. Description of the Related Art.
A device of the above type is already known from Swedish Patent specification 8900391-7 or from the corresponding U.S. Pat. No. 4,920,843 and it functions with excellence if the knife blades have the required dimensions.
By setting the wedge device such that its height position in the slot is adapted to the required dimension of the knife blade, efficient wedging-up of said knife blade is obtained as well as an exact predetermined position thereof.
However, it has been noticed that knife blades, for various reasons, in some cases do not have the required dimensions, but the height thereof can vary, for examples, within the tolerance interval .+-.0.2 mm and/or the thickness within the tolerance interval .+-.0.1 mm. If the knife blades have dimensions lying at the limits of said tolerance intervals, there is a risk that they are either not properly wedged up or that they are wedged up too high up in the slot. This can result in these knife blades loosening from the slot or damaging the counter pressure cylinder or the material to be treated.